1. Field of the Invention
The present invention relates to a differential amplifier that amplifies or compares an inputted voltage.
2. Description of the Related Art
In recent years, along with the progress in a digital processing technology of video signals there is a growing demand of high performance in an analog-to-digital converter circuit (hereinafter referred to as “A/D converter” also) used in the video signal processing. As an A/D converter that meets this demand, an A/D converter of a pipeline type has been utilized.
The pipeline type A/D converter is configured by including a sub-A/D converter and a digital-to-analog converter circuit (hereinafter referred to as “D/A converter” also). The sub-A/D converter is of a flash type, capable of performing high-speed conversion, where comparators are all connected in parallel. The sub-A/D converter is configured by including a plurality of differential comparators that compare a plurality of reference voltages with an input voltage. The conventional differential comparator is configured such that the switches within a circuit are CMOS switches (transfer gates). In such CMOS switches, parasitic capacitances exist between sources and gates or between gates and drains. Hence, switching noise dependent on the input voltage occurs when the switch is turned on and off. Then a problem arises where this switching noise is transferred to an output by way of the parasitic capacitance.